1. Field of the Invention
The present invention relates to an improved propeller driven snow vehicle.
2. Description of the Prior Art
Prior attempts to develop a sport vehicle capable of safely and efficiently traversing terrain covered with snow and ice have generally continued along two lines: snowmobiles and air driven ski vehicles. Snowmobiles are by far the more common of the two with their endless track propulsion systems and motorcycle style bodies. Air powered vehicles are much rarer, and have in the past, conceptualized along a three ski theme design.
U.S. Pat. No. 2,905,479 issued to Schomers on Sep. 22, 1959 shows one such three ski vehicle with rear skis mounted on a complex parallelogram support to each other to provide simultaneous tilting of the two rear skis to mimic the slant of the terrain. Braking is provided by a drag brake.
U.S. Pat. No. 3,785,330 issued to Fox on Jan. 15, 1974 shows an air driven vehicle generally modeled after an airplane and includes three skis and a coil spring shock absorber retarding the downward movement of the two rear skis.
U.S. Pat. No. 3,841,649 issued to McMullen on Oct. 15, 1974 shows an open carriage pontoon-mounted vehicle with a rear mounted prop. Two side skis stabilize the vehicle, and steering is performed through a steerable ski mounted under the front portion of the pontoon.
U.S. Pat. No. 3,814,197 issued to Milankov et al. on Jun. 4, 1974 shows a skate mounted vehicle with a rear mounted fan. The single front skate is mounted on a pivot to provide steering control over the vehicle. Canadian patent 950,008 to Milankov et al. issued on Jun. 25, 1974, related to U.S. Pat. No. 3,814,197, discloses a three skated vehicle.
U.S. Pat. No. 3,861,492 issued to Jensen, Sr. on Jan. 21, 1975 shows a motorized ice-bike with three skates. A cable operated drag brake is attached to each rear ski to provide braking.
U.S. Pat. No. 4,189,019 issued to Zech on Feb. 19, 1980 shows a propeller-type propulsion unit mounted on the back of a skier by a suitable harness.
U.S. Pat. No. 4,260,036 issued to Bissett on Apr. 7, 1981 shows a powered ski vehicle mounted on a single runner. The angle of thrust provided by the prop engine can be varied to assist in steering the vehicle. In separate embodiments elevated pontoons provide lateral support to prevent the vehicle from tipping over.
U.S. Pat. No. 4,342,372 issued to Hayes on Aug. 3, 1982 shows a telescoping suspension on a snowmobile which has an internal shock absorber to limit compression of the telescoping arm connecting a front ski to the body of the snowmobile.
German Patent 1,927,405 to Nelson published on May 5, 1969 discloses a three skated vehicle with a single, front steerable skate.
The use and success of these three runner vehicles has been extremely limited in the past because of stability and responsiveness problems, as well as higher costs associated with these air powered vehicles. Prior designs of the three ski vehicle have been developed from modified airplane designs, rather than the more stable land vehicle designs. Aerodynamic factors have been given more design weight than the more practical aspects such as stability and steering control.
When a vehicle with one front ski maneuvers through a tight turn, the outside front corner of the vehicle can dip under the force of the centrifugal load, promoting the lifting of the opposite rear corner, threatening, and sometimes causing, tipping of the vehicle. In a best case scenario, the vehicle experiences tremendous understeer as the center of the loading of the steering moves away from the center ski towards the lowered corner of the vehicle. In answer to this instability which is inherent with a three-ski design, complicated devices have been developed such as the bulky rear parallelogram suspension shown in the Schomers patent, which compensate for the lack of stability of the vehicles.
In great contrast, the vehicle of the present invention overcomes these prior shortcomings and provides stability and mobility not present in the earlier devices. By implementing a four ski design with two front steerable skis, the vehicle gains a unexpected stability and control above and beyond the prior vehicles. By building a vehicle with two front skis and a broader base, the vehicle is much less likely to tip or roll during a turn.
With a four ski vehicle, the centrifugal force directs more weight to the outside front ski during a turn, increasing the friction between the ski and the terrain, assisting the ski in engaging the terrain to enhance the turning, rather than detracting from it. The outside ski, together with the suspension system connecting the ski to the vehicle, resist the rolling forces caused by turning and increase the stability of the machine. The four-ski vehicle is unique among the air driven vehicles and provides a new and exciting alternative to the mainline snowmobiles currently being produced.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.